A dot matrix type liquid crystal panel, in which a plurality of display picture elements are two-dimensionally arranged in a matrix form, for instance, is usually employed as a display device for a mobile electronic apparatus, such as a mobile telephone or a pager. In such an apparatus, a display control device, configured as a semiconductor integrated circuit, a driver for the liquid crystal panel or a display control device with a built-in driver is mounted for controlling displays on this liquid crystal panel. Some of these display control devices may have a rewritable random access memory (RAM) built in for storing data to be displayed on the liquid crystal panel. Upon receiving display data from a microprocessor controlling the whole apparatus or processing transmit/receive signals, the display control device rewrites display data in the internal RAM (hereinafter to be referred to as the display RAM).
More specifically, as shown in FIG. 11, data such as 1 word (16 bits), supplied from the microprocessor via buses BUS0 through BUS15 are successively taken into latch circuit groups LTG1 through LTG4, provided to match bit lines of the display RAM 140, in synchronism with timing signals φ11, φ12 . . . shown in FIG. 12. Transfer gate groups TGT1 through TGT4, provided between the latch circuit groups LTG1 through LTG4 and the display RAM, are successively opened in accordance timing signals φ31, φ32 . . . , and data are successively written into the display RAM 140 word by word. This has been the usual way of processing.
The demand for the display of moving pictures on a display screen of a mobile telephone has been increasing in recent years. As a display device of this type, a liquid crystal display device, an organic EL display device, a plasma display device or a field emission type display device, etc., are known. However, since the existing mobile telephone has been mainly used to display still pictures including a text, a drive control circuit thereof is only provided with a still-picture-text-system-I/O-interface and does not comprise an interface corresponding to moving pictures. Accordingly, the existing drive control circuit is capable of displaying moving pictures but it is difficult for such circuit to display moving pictures in higher picture quality which can be seen smoothly.
FIG. 33 is a block diagram for explaining an example of a drive circuit system configuration of a mobile telephone having no interface corresponding to moving pictures which is an example of a display drive control circuit and display device. This display drive control circuit system 201′ is configured with an audio interface (AUI) 202, a high frequency interface (HFI) 203, a picture processor 204′, a liquid crystal controller driver-driver (LCD-CDR) 206′ as a memory 205 and a display drive control circuit and a still-picture-text-system-I/O bus-interface (SS/IF) 207, etc. Reference numeral 209 designates a microphone (M/C); 210, a speaker (S/P); 212, an antenna (ANT); 213, a liquid crystal panel (liquid crystal display; LCD).
The picture processor 204′ is configured with a baseband processor 241 including a digital signal processor (DSP) 411, an ASIC 412 and a microcomputer MPU. The audio interface (AUI) 202 controls prefetch of an audio input from the microphone 209 and output of an audio signal to the speaker 10.
For the display to the liquid crystal panel 213, picture data is read from the memory 205 and is subject to the necessary processes in the microcomputer MPU 413. Thereafter, the picture data is then written into the display RAM within the liquid crystal controller driver (LCD-CDR) 206′. In the moving picture display mode, 10 to 15 frames are changed within a second. In this system, a system I/O bus represented by the 80-system interface is used. The still-picture-text-system-I/O bus-interface (SS/IF) 207 is referred to as system interface 207 in a certain case.
Display operation in the liquid crystal controller driver (LCD-CDR) 206′ is realized with a built-in clock thereof. Therefore, write operation of picture data and display operation thereof are performed asynchronously.